This post will show how to simulate cellular automata using shaders. The popular cellular automaton developed by John Conway, Game of Life, will be used as an example for this tutorial. To learn how to set up your project, check out the first two parts of this tutorial: How to Use Shaders For Simulations and How to Simulate Smoke with Shaders.
This tutorial explains how to pass arrays to shaders in Unity. This feature has been present for a long time, but is mostly undocumented. Unity 5.4.0 Beta 1 will introduce a proper API to pass arrays to shaders; this technique however will work with any previous version.
The previous three posts of this tutorial have introduced surface shaders and how they can be used to specify physical properties (such as albedo, gloss and specular reflections) of the materials we want to model. The other type of shader available in Unity3D is called vertex and fragment shader. As the name suggests, the computation is done in two steps. Firstly, the geometry is passed through a function called (typically called
vert) which can alter the position and data of each vertex. Then, the result goes through a
frag function which finally outputs a colour.
We can safely say that Unity3D has made game development easier for a lot of people. Something where it still has a long way to go is, with no doubt, shader coding. Often surrounded by mystery, a shader is a program specifically made to run on a GPU. It is, ultimately, what draws the triangles of your 3D models. Learning how to code shaders is essential if you want to give a special look to your game. Unity3D also uses them for postprocessing, making them essential for 2D games as well. This series of posts will gently introduce you to shader coding, and is oriented to developers with little to no knowledge about shaders.
The diagram below loosely represents the three different entities which plays a role in the rendering workflow of Unity3D: